The major objective of the proposed research is to develop a computer model that predicts the prevalence of the HIV infection and the progression of HIV to the AIDS disease. A significant feature of the model will be to portray the role of IV drug use in the spread of AIDS. In particular, the influence of IV drug users on the spread of HIV to AIDS heterosexual risk groups will be examined. In summary, the proposed research will: o Project HIV and AIDS disease prevalence in the total population o Project the proportion of the HIV prevalence and AIDS disease cases that are IV drug users o Project the number of new infections resulting from IV drug use o Project the size of the infected heterosexual population o Project the new HIV infections in the heterosexual risk group that are spread by IV drug users. Disease transmission characteristics in general are highly nonlinear and as a consequence are counter intuitive. Identifying appropriate policies for managing the AIDS epidemic is critical at this time. However, reliance on existing AIDS models identified in the literature is inappropriate. The major reason is that many of the models and/or model parameters are wedded to historical behavior patterns. As a result, they do not directly account for: o All of the primary transmission routes, i.e., homosexual contact, IV drug use, and heterosexual contact o The linkages between transmission interruption and control strategies such as education awareness programs or vaccines and therapy programs o The major risk group characteristics behavior that influence transmission o Observed trends in behavior modification that are influencing transmission. The proposed computer model will account for all of the above.